Did you read any of the "Long Earth" series, by Terry Pratchett and Steven Baxter? I thought they were a fascinating addition to Terry Pratchett's range, late in his career.
Jasper Fforde
http://www.jasperfforde.com/index.html will appeal to the same readership - the subject matter is very different, but the humour has the same sort of "edge". There are three main series worth looking into:
Thursday Next - about a detective who works in Jurisfiction, whose job it is to make sure that all of the characters in works of fiction "stick to the plot".
Nursery Crime - DCI Jack Spratt and Sergeant Mary Mary investigate crimes within the world of nursery rhymes.
Shades of Grey - set in a post-apocalyptic future in which social status is determined by one's colour perception. (I found this one particularly interesting, as I am red-green colour-blind, which would put me only one rung above the "untouchables" who can only see in black and white.)
